The present invention relates generally to data networking and, more specifically, to Y-cable protection enhancement in supporting Fibre Channel distance extension.
SONET/SDH and optical fiber have emerged as significant technologies for building large scale, high speed, Internet Protocol (IP) based networks. SONET, an acronym for Synchronous Optical Network, and SDH, an acronym for Synchronous Digital Hierarchy, are a set of related standards for synchronous data transmission over fiber optic networks. SONET/SDH is currently used in wide area networks (WAN) and metropolitan area networks (MAN). A SONET system consists of switches, multiplexers, and repeaters, all connected by fiber. The connection between a source and destination is called a path.
One network architecture for the network interconnection of computer devices is Fibre Channel, the core standard of which is described in ANSI (American National Standards Institute) X3.230-1994. The Fibre-Channel standard defines a bi-directional link protocol, used to connect computers to disk drives and other peripherals. Arising out of data storage requirements, Fibre Channel currently provides for bi-directional gigabit-per-second transport over communication networks in Fibre Channel frames that consist of standardized sets of bits used to carry data over the network system. Fibre Channel links are limited to no more than 10 kilometers.
New standards and protocols have emerged to combine the advantages of the SONET/SDH and Fibre Channel technologies. For example, it is sometimes desirable to link two SANs (Storage Area Networks), which operate with Fibre Channel protocol, over a MAN (Metropolitan Area Network), or even a WAN (Wide Area Network), which typically operates under SONET or SDH standards. The advent of high data rate metropolitan optical networks including such networks based on the use of dense wave division multiplexing (DWDM) and/or SONET/SDH transport systems makes it possible to extend so-called storage area networks (SANs) that carry multiple Fibre-Channel links over distances much longer than 10 kilometers. This extension of Fibre Channel from 100 kilometers to over several hundred, or even thousand, kilometers, is made by mapping Fibre Channel ports to a SONET/SDH path for transport across a SONET/SDH network.
Y-cable protection scheme in Fibre Channel is designed as one way traffic protection. Near End (NE) equipment and Far End (FE) equipment within a network can provision Y-cable differently and can act independently. This means that NE and FE equipment may be in different configurations and in different states (e.g., Manual Switch/Forced Switch/Reverse Request, Active/Standby State, Working/Protect, etc.). Due to the nature of Fibre Channel, when Fibre Channel Distance Extension (DE) is enabled, DE control state machine has to be working only with bi-directional traffic. This requires the NE trunk to communicate with the FE trunk over a SONET path and both receive and transmit Fibre Channel traffic have to go through the same path (trunk).
There is, therefore, a need for a method and system that allows Distance Extension, or other features requiring bi-directional traffic, to function properly in networks configured for one-way traffic protection such as Y-cable protection.